Test with go 1.20/ go 1.21

[arukiidou]

goals

Go 1.21 is released. add test with go 1.20 / go 1.21

tasks

• [x] add matrix test
• [x] test with go 1.20/ go 1.21

non-goals

• bump actions/setup-go and actions/checkout
• drop go 1.19

sample

https://github.com/actions/setup-go#matrix-testing

[ericchiang]

Fixed with #419